Many types of implantable leads are currently used to treat a variety of maladies. Two common treatment applications use leads having multiple electrode contacts. Cochlear stimulator systems use a multiple electrode contact lead inserted into one of the cochlear chambers to stimulate the cochlear nerve. Another application where a multiple electrode contact lead is used is the treatment of chronic pain through stimulation of the spinal cord.
Spinal cord stimulation systems generally have two implantable components: an implantable pulse generator (IPG) and at least one lead connected to one output of the PG. Generally, however, the IPG is a multi-channel device capable of delivering electrical current through the electrode contacts of the lead. The term “lead” used herein will refer to an elongate device having any conductor or conductors, covered with an insulated sheath and having at least one electrode contact attached to the elongate device, usually at the distal portion of the elongate device. The lead can have an inner stylet lumen running through most of the length of the lead and which lumen has an opening at the proximal end of the lead. A stylet may be placed into this stylet lumen during steering and implantation of the lead. The inserted stylet in the lumen can help stiffen the lead so that the stylet/lead combination may be more easily inserted through tissue.
There are two types of leads that may be used with the IPG. The first type is a paddle lead, which has a multiplicity of electrode contacts spread out over a flat, paddle-like surface that is attached to one end of the lead. A paddle lead advantageously permits the electrode contacts to be spaced apart to provide wide coverage over a stimulation area. A disadvantage presented with a paddle lead is that it usually requires a laminectomy or laminotomy, which are highly invasive surgical procedures necessary to implant the large, non-isodiametric paddle.
A second type of lead that is commonly used is a percutaneous lead, which has multiple electrode contacts positioned along the distal portion of an elongate lead. U.S. Pat. No. 6,205,361 issued to Baudino et al, describes the making of a multi-contact electrode array for a lead. The distal end of the lead may be about the same thickness or diameter as the remainder of the lead. The percutaneous lead is dimensionally configured for tunneling to a target stimulation site. No invasive surgical procedure such as a laminotomy is required; the percutaneous lead may be placed through an epidural type needle reducing surgical trauma.
The method of making a multi-contact percutaneous lead can be involved. In general, it is desirable to make the lead efficiently, with the fewest number of process steps, maximize the manufacturing yield, and hence reduce the cost of goods of building the leads. There is thus a continual need to improve the design of a percutaneous lead in order to improve its performance and to improve the method of manufacturing the lead.